This is the kind of film to get the blood boiling and the steam hissing out of your ears. Campaigning journalist Mark Donne has constructed an ambitious and admirably clear assault on the UK's lamentable record in the tax avoidance industry, zeroing in on the unsavoury role played by the City of London and its institutions – not just in this country, but in far more desperate international territories too. In fact, one of the more sinister allegations of this film concerns TheCityUK, a body set up by our own Square Mile, which is using its clout to develop the Kenyan capital Nairobi as a financial hub.

With the assistance of a string of well-informed talking heads, Donne's film points out the major features of the tax avoidance landscape: tax havens, brass plates, capital flight, crown dependencies, and the like. It soon becomes clear that the avoiders' best weapon is silence – the list of those who refused to talk to the film-makers, helpfully appended to the closing credits, speaks volumes. Operating under the media radar, and taking advantage of the jurisdiction-hopping only the super-rich are capable of, this specialised skill set liberates a staggering amount of money from national treasuries, whichever way you look at it.

Donne's film offers a harsh verdict on the current UK government; despite its protestations to the contrary, it has introduced legislation to make it easier to avoid tax abroad. Barack Obama, in contrast, comes in for a fairly glowing assessment, condemning the arrangements in certain UK-controlled territories as a "scam" and setting up tough regulations for anyone doing business with US companies.

This is a knotty, complex theme, and certainly of vital, topical import; Donne does his best to keep it stimulating to watch, even if he has to resort to lots of helicopter shots of a jewel-box City of London and other visual filler. Worried, perhaps, that his film isn't dynamic enough, Donne introduces a telegenic cleric, the Rev William Taylor, who is supposedly orchestrating the film's investigation; after a brief scene-setting he promptly disappears and doesn't re-emerge until the 40-minute mark. In truth, gallant though Taylor is, his presence isn't really necessary.

Be that as it may, this is a documentary to outrage and appal. Whether it can trigger actual change remains to be seen; its best hope is that, in any follow-up report, narrator Dominic West will not have to intone, as he regularly does here, "This was not reported in any national media."